The human hand includes fourteen phalanges, five metacarpal bones, and eight carpal bones. The fourteen phalanges form the bony structure of the fingers and the thumb. The index finger, middle finger, ring finger, and small finger each include a proximal phalanx bone, an intermediate phalanx bone, and a distal phalanx bone and the thumb includes a proximal phalanx bone and a distal phalanx bone. With respect to the fingers, distal interphalangeal joints are formed between the distal phalanges and the corresponding intermediate phalanges and proximal interphalangeal joints are formed between the intermediate phalanges and the corresponding proximal phalanges. Metacarpophalangeal joints are formed between the proximal phalanges of the fingers and the corresponding metacarpal bones. With respect to the thumb, a distal interphalangeal joint is formed between the distal phalanx bone and the corresponding proximal phalanx bone. A metacarpophalangeal joint is formed between the proximal phalanx bone of the thumb and the corresponding metacarpal bone.
The interphalangeal joints and the metacarpophalangeal joints articulate, somewhat independently of one another, and the carpal bones allow for intercarpal articulation of the wrist. Each finger is capable of bending independently of one another towards the palm of the hand. The thumb is opposable such that it may be brought to meet one or more of the fingers. Bony arches of the hand, such as longitudinal arches formed by the phalanges and their corresponding metacarpal bones, transverse arches formed by the carpal bones and distal ends of the metacarpal bones, and oblique arches formed by the thumb and the fingers, allow for the fingers and the palm of the hand to curve around objects. As a consequence, the human hand is a precise instrument capable of a diverse range of motions and poses, including the ability to grasp one or more objects with varying degrees of pressure.